Linear Drive Wrap Spring Clutch for Emergency Bed Lowering
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Solution Overview
Problem
Existing electromotive linear drives for furniture are complex, difficult to operate, and do not allow for quick and reliable emergency power failure lowering mechanisms, especially in hospital and care settings where ease of use and robustness are critical.
Innovation Solution
A simplified linear drive design featuring a spindle nut with a cylindrical outer circumference, a rotatable actuating ring, and an actuating bar that allows for easy manual or remote-controlled activation of the wrap spring clutch to release the lifting element, enabling quick and convenient lowering of furniture parts in emergencies or power failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a manual operating handle is provided directly behind the connection to the lifting element for operating the wrap spring clutch, then the wrap spring clutch can be operated to lower the furniture part, but handling is extremely inconvenient and difficult, especially when the linear drive is arranged below a hospital bed
Solution Approach 1:
An actuating bar is introduced as an intermediary element that extends the actuating ring's functionality to a more accessible location. The actuating bar can be operated from outside the bed, eliminating the need to reach behind the bed to operate the wrap spring clutch. This mediator transfers the operating force from a convenient location to the clutch mechanism.
Solution Approach 2:
The actuating mechanism is extended from a purely radial operation (at the actuating ring) to include an axial component through the actuating bar. This dimensional extension allows the operator to access and operate the clutch from a different spatial dimension, specifically from outside the bed rather than from behind it.
2Strength
If the linear drive uses a complex mechanism with multiple components for the speed reduction gear and coupling, then the drive can be assembled and operated, but the construction is relatively complex and cannot be loaded as desired
Solution Approach 1:
The actuating ring and actuating bar are merged into a single integrated actuating mechanism. The actuating bar is directly connected to the actuating ring, combining the rotational and linear actuation functions into one unified component assembly. This reduces the number of separate parts and simplifies the overall construction.
Solution Approach 2:
The actuating bar serves multiple functions: it acts as an extension of the actuating ring for remote operation, provides a lever arm for increased mechanical advantage, and serves as a structural support element. This multi-functionality reduces the need for separate components and simplifies the overall mechanism.
3Reliability
If the thread between the spindle and the spindle nut is not self-locking to allow automatic return to lowered position, then emergency lowering is enabled, but the drive mechanism cannot maintain position without continuous power
Solution Approach 1:
The non-self-locking thread allows the spindle nut to automatically return to its lowered position through the force of gravity when power is failed or the drive is released. The system uses its own weight and gravitational force to automatically reset to the safe lowered position without requiring external intervention or additional locking mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a robust, easy-to-assemble, and user-friendly mechanism that ensures furniture parts can be quickly and reliably lowered in emergency situations, with a continuous drive train capable of transmitting larger forces and a long-lasting wrap spring clutch with optimal friction properties.
Implementation Method 1
a wrap spring (16) is provided as a coupling between the lifting element and the spindle nut
Implementation Method 2
a threaded spindle (5), a speed reduction gear arranged between the drive motor and the threaded spindle
Implementation Method 3
the wrap spring tightly surrounding the spindle nut in its normal state and connecting it to the lifting element in a torque-proof manner
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an electric linear drive, in particular for adjusting movably mounted parts of furniture used for sitting or lying down, comprising a drive motor, a threaded spindle (5), a speed reduction gear arranged between the drive motor and threaded spindle (5), a spindle nut (6) which is placed on the threaded spindle (5) and can be selectively locked in the direction of rotation and, depending on the direction of rotation of the threaded spindle (5), moved in the axial direction of the threaded spindle (5). The linear drive further comprises a lifting element (7) for adjusting the movable furniture parts, said lifting element (7) being driven by the axial movement of the spindle nut (6). The aim of the invention is to simplify the design of the linear drive, make the linear drive easy to assemble and operate, and ensure robust mounting of the driving parts. Said aim is achieved by the fact that the drive wheel (4) of the speed reduction gear is fixedly connected to the threaded spindle (5), the lifting element (7) is guided in the axial direction of the threaded spindle (5) so as to be rotationally locked with respect to the longitudinal axis of the lifting element, and the spindle nut (6) can be coupled in such a manner to the lifting element (7) driven in a rotationally locked manner that the spindle nut can be selectively connected to the lifting element in a rotationally locked manner or removed therefrom.